Transcript No Slide Title

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Lecture 19, 04 Nov 2003
Chapter 13, Respiration, Gas Exchange, Acid-Base Balance
Vertebrate Physiology
ECOL 437
University of Arizona
Fall 2003
instr: Kevin Bonine
t.a.: Bret Pasch
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Vertebrate Physiology 437
VOTE!
1. Blood-Gas Chemistry
(CH13)
2. Announcements...
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Term Paper Draft due Thursday 06 Nov.
Turn in old, relevant, graded work.
On the actual most recent draft use a
CODE NAME so your paper can be
anonymously reviewed by one of your
peers.
We will give you a paper to edit/review at
the end of class on Thursday
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Name that student:
Jane Davis
Hematology
Oncology
French
Katie Cox
Tall
Kim Hurd
Air Force ROTC
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Gravity
and BP
Knut Schmidt_Nielsen 1997
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Cardiac Output 6x
Exercise
Oxygen
Consumption
X 20
Knut Schmidt_Nielsen 1997
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Chapter 13 – Blood-Gas Chemistry
Oxygen and Carbon Dioxide
- Air vs. Water
- Epithelial Transfer
- Transport and Regulation
pH regulation
Chloride shift
Carbonic Anhydrase
Elevation
Skip: Diving, Swimbladder, Exercise
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Gas composition in air
O2
CO2
N2
% of dry air
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0.03
78
159
0.23
594
0.11
297
1,019
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pp at 760 mm Hg
380mmHg (at 6000m)
79.6
Solubility in water (ml/L)
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Why is pO2 in lungs less than ‘expected’?
Effects of Temp and Solutes on O solubility
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Temp (C)
Fresh
Sea
0
10.29
7.97
10
8.02
6.60
20
6.57
5.31
Increase in temp
decrease solubility
Increase [ion]
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Rate of diffusion depends on molecular weight (Graham’s Law)
Air
Water
O 2 solubility
>
O 2 rate of diffusion
>
Weight of medium
<
(amt. needed to get O2 )
Movement of medium
tidal
(take in,
expel)
unidirectional
(less energy
required)
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Gas transfer
1. Breathing (supply air or water to respiratory
surface)
2. Diffusion of O & CO across resp. epithelium
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2
(humans = 50-1002 m
3. Bulk transport of gases by blood
4. Diffusion across capillary walls (blood
mitochondria)
SA)
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13-1
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Gas transport in blood
Respiratory pigments
all have either Fe2+or Cu2+ ions that O2 binds
pigment increases O 2content of blood
complex of proteins and metallic ions
each has characteristic color that changes w/ O 2
content
• ability to bind to O2 (affinity) affects carrying
capacity of blood for O 2
•
•
•
•
98% of O 2 transported via carrier
molecules
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hemoglobin
Metal
Distribution
Location
Color
Fe2+
over 10 phyla
(all verts, many inverts)
RBCs (verts)
deox – maroon
ox – red
hemocyanin
Cu2+
hemerythrin
Fe2+
2 phyla
4 phyla
(arthropods, mollusks)
dissolved in
plasma
colorless
blue
intracellular
colorless
reddish violet
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Hemoglobin
and other
Respiratory
Pigments
Knut Schmidt_Nielsen 1997
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hemoglobin
4 heme + 4 protein chains
can carry 4 O2
heme
molecules
hemoglobin
Fetal hemoglobin:
γ chains (not β) w/ higher affinity for O 2
(enhance O 2transfer from mother to fetus)
Affinity for CO = 200 x’s greater than for O 2
CO poisoning even at low partial pressures
Antarctic icefish lack pigment
low metabolic needs = low metabolism
high cardiac output, blood volume
large heart
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O 2 dissociation curve
hyperbolic
sigmoidal
• not need lots of O 2 to get near 100%
Cooperativity
-binding of 1st O2 facilitates more binding
-oxygenation of 1st heme group increases
affinity of remaining 3 for O2
P - pp of O at which pigment is 50% saturated
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2
Pigment w/ High P
50
:
• low affinity
• high rate of O transfer to
tissues 2
Pigment w/ Low P
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• high affinity
:
• high rate of O uptake
2
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Factors that reduce affinity
1. low pH (increase [H+])
2. increase in CO2
3. elevated Temp
4. organic compounds
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Factors that reduce affinity
1. and 2. Increase in [CO 2 ] or [H+]
• Bohr effect
CO 2 and H + bind to hemoglobin (allosteric site), which
changes conformation of molecule and
changes binding site for O 2
at tissues:
CO 2 binds to hemoglobin, decreasing affinity
for O2 , allowing better delivery of O 2
• Root effect
fishes… (skip)
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Bohr Effect
CO2 enters blood at tissues
hemoglobin unloads O 2
CO2 leaves blood at resp. surface
hemoglobin uptake O2
CO + H O
2
Inc in Pco 2
2
inc [H+]
H CO
2
3
H+ + HCO-
dec pH
3
reduces affinity
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Bohr shift
as a
function of
body size
(small animals with
greater Bohr shift
[more acid sensitive]
so can more readily
leave oxygen at
tissues at given PO)
Knut Schmidt_Nielsen 1997
Factors that reduce affinity
4. organic compounds
• organophosphates in erythrocytes differ among spp.
mammals: 2,3 DPG
birds: IP3
fish: ATP, GTP
• bind to hemoglobin as allosteric effectors
• used to maintain O2 affinity under hypoxic conditions
at high altitude (low blood [O 2])
to increase delivery 2of O to tissues
increase 2,3 DPG
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CO 2 transport in blood
CO 2 + H2 O
H2CO3
CO2 + OH -
H +
+
HCO3
HCO3-
Proportions of CO2 , HCO 3- depend on pH, T, ionic strength of blood
At normal pH, Temp:
-
80% of CO 2 in form of bicarbonate ion HCO3
5-10% dissolved in blood
10% in form of carbamino groups
(bound to amino groups of hemoglobin)
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Haldane effect
• deox hemo has high affinity
for H creating inc.
[HCO
3
] in blood (more2 CO )
+
•recall equations on previous
slide
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Bohr effect + Haldane effect
increasing [CO2 ] decreases affinity of
hemoglobin for O2 , so binds CO2 more easily
CO 2 transfer at tissue
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-Chloride Shift
-Carbonic Anhydrase
• enters/leaves blood as CO 2 (more rapid diffusion)
• passes thru RBCs
• CO produced = O released
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oxygenation
of hemo:
acidify
interior
(release H +)
only in
RBC, not
plasma
2
no change in pH
Band III
protein
passive
exchange,
bidirectional
maintain
charge balance
deox of hemo:
+
inc pH (bind H )
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CO 2 transfer at lung
facilitated
diffusion
Acidify RBC:
facilitate
HCO3CO2
-
dec. in HCO3 in
RBC:
influx
Acid-Base balancing
• Animal body pH: slightly alkaline (more OH - than H+)
• maintain pH for stability of proteins (and function)
H+production / excretion
• produced: metabolism of ingested food
ingest meat: acid
ingest plants: base
small overall effect
on pH
• excreted continually via kidneys, gills, skin
• build-up of CO
• low CO2
2
build-up of H + (acidify body)
low H+ (alkaline body)
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pH buffers in blood:
bicarbonate – not true buffer, but CO 2/ HCO 3-ratio imp. to pH
excretory organs (kidneys, gills, skin)
proteins (hemoglobin), phosphates
CO 2+ H2 O
H2CO3
+
-
H + HCO 3
Respiration and pH
• inc. lung ventilation (low body [CO ])
2
respiratory alkalosis
inc pH
buffer: kidney dec. pH by excreting HCO 3
• dec. lung ventilation (CO excretion dec.)
dec. pH
2
respiratory acidosis
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pH buffers
If CO 2 inc in extra., diffuse
into cell
to form HCO 3 and dec.
intracellular pH
efflux of H +, or influx of HCO 3leads to rise in pH
via ATPase or
+
coupled w/ Na
influx
Muscle vs. Brain
Need to REDO:
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Response to acid load in cell:
• H+efflux + Na influx (cation-exchange)
• H+passive diffusion out of cell
or both in
plasma
membrane
• HCO 3 influx + Cl efflux (anion-exchange)
• H+efflux = HCO -3 influx
HCO3- inside cell
CO 2+ OH - (inc. pH)
Jacob-Stewart
-+ H +
CO
leaves
cell
to
form
HCO
2
cycle p.543
3
• buffering via proteins/phosphates in cell
Maintaining pH balance in the body
(acid production = acid excretion)
Mammals: adjust
CO 2 excretion via lungs
-
acid/HCO 3 excretion via kidneys
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Jackson et al. 2000
Apalone - softshell turtle
Chrysemys - painted turtle
Mg+, Ca+ (weak base carbonates)
Lactic acid
bone sequestration
anoxia
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Lung Anatomy
Nonrespiratory
-Trachea ->
-Bronchi ->
-Bronchioles ->
Respiratory
-Terminal
bronchioles ->
-Respiratory
bronchioles ->
-Alveoli
-Cilia and Mucus
(13-21)
-Gas Diffusion Barriers:
(13-22)
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Lung Ventilation
-Small mammals with greater per
gram O2 needs and therefore greater
per gram respiratory surface area
-Dead Space (anatomic and physiological)
Swan
(13-24)
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Lung
Ventilation
(13-23)
End